This application claims the benefit of Korean Application No. 2003-32287, filed May 21, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary compressor, and more particularly, to a variable capacity rotary compressor capable of varying compression capacity of a refrigerant.
2. Description of the Related Art
In recent years, refrigeration systems, used in air conditioners or refrigerators, usually include a variable capacity rotary compressor, which is designed to allow variation of a compression capability of refrigerant in order to achieve an optimal refrigeration capability, thus meeting requirements and saving energy.
U.S. Pat. No. 4,397,618 discloses a variable capacity rotary compressor, which is adapted to control a compression capability thereof by locking or releasing a vane. The variable capacity rotary compressor includes a casing having a cylindrical compressing chamber therein, and a rolling piston disposed in the compressing chamber of the casing to be eccentrically rotated. The casing is provided with a vane, which is radially movable back and forth while being in contact with an outer surface of the rolling piston. Adjacent to the vane, a locking unit including a ratchet bolt, an armature and a solenoid is provided to control a compression capability of the rotary compressor by locking or releasing actuation of the vane. More specifically, the vane is locked or released by the ratchet bolt which is moved back and forth by the solenoid, thereby varying a compression capability of the rotary compressor.
However, since the above variable capability rotary compressor is constructed to control a compression capability in such a way that a compressing operation is blocked by locking the vane for a certain period and the compressing operation is allowed by releasing the vane for a certain period, it is difficult to vary a compression capability into a desired discharge pressure.
Accordingly, an aspect of the present invention provides a variable capability rotary compressor, which can easily perform and precisely control the variation of a compression capability into a desired discharge pressure.
It is another aspect of the present invention to provide a variable capability rotary compressor, which is designed to minimize resistance to rotation so as to enhance a compression capability thereof.
The foregoing and/or other aspects of the present invention are achieved by providing a variable capacity rotary compressor, including a hermetic casing, a housing disposed in the hermetic casing and including first and second compressing chambers having different capacities, a rotating shaft rotatably disposed in the first and second compressing chambers, first and second eccentric units mounted on an outer surface of the rotating shaft in the first and second compressing chambers, the first and second eccentric units being operated in opposite manners such that when either the first or second eccentric unit is locked in an eccentric state to perform a compressing operation, the other eccentric unit is released from the eccentric state to release the compressing operation, first and second roller pistons fitted on outer surfaces of the first and second eccentric units, respectively, first and second vanes provided in the first and second compressing chambers to be radially moved while being in contact with the first and second roller pistons, respectively, and a pressure control unit to allow a discharging pressure to be applied to either the first or second compressing chamber, where an idle rotating operation is performed.
The pressure control unit may include first and second flow paths communicating with the first and second compressing chambers to allow a discharging pressure to be applied to either the first or second compressing chamber, where an idle rotating operation is performed, and first and second valves provided at the first and second flow paths to open and close the flow paths.
The pressure control unit may include a connecting pipe provided outside the hermetic casing to communicate with an inside of the hermetic casing, and wherein the first and second flow paths are defined by first and second branch pipes diverging from the connecting pipe, the first and second valves being provided at the first and second branch pipes.
The pressure control unit may include a connecting pipe provided outside the hermetic casing to communicate with an inside of the hermetic casing, first and second branch pipes diverging from the connecting pipe and communicating with the first and second compressing chambers, and a three-way valve provided at a diverging point where the first and second branch pipes diverge from the connecting pipe.
The housing may include an intermediate plate to isolate the first and second compressing chambers from each other, and the pressure control unit may include a path-diverting chamber formed in the intermediate plate and having first and second through-holes communicating with the first and second compressing chambers, a communicating path to allow an inside of the hermetic casing to communicate with the path-diverting chamber, and a valve piece disposed in the path-diverting chamber and operated by a pressure difference between the first and second compressing chambers to close either the first or second through-hole where a compressing operation is performed while opening the other through-hole.
The communicating path may include a connecting pipe extended from the hermetic casing to communicate with an inside of the hermetic casing, and a flow path radially formed in the intermediate plate to be connected between the path-diverting chamber and the connecting pipe.
The first and second through-holes of the path-diverting chamber may be provided at a position opposite to the first and second vanes.
Diameters of the path-diverting chamber and the valve piece may be larger than those of the upper and lower through-holes so as to enable the valve piece to close the upper and lower through-holes.
The valve piece may be made of a thin resilient plate.
The variable capacity rotary compressor may further include a path-diverting unit to allow refrigerant to be drawn into either one of inlet ports of the first and second compressing chambers, where a compressing operation is performed.
The path-diverting unit may include a hollow body, having a predetermined length, closed at opposite ends thereof, an inlet opening provided at the center of the hollow body, first and second outlet openings provided at the side opposite to the inlet opening with a spacing therebetween, and communicating with the inlet ports of the first and second compressing chambers, respectively, a hollow valve seat disposed in the hollow body to communicate with the inlet opening and having opposite ends communicating with the first and second outlet openings, and first and second valve members movably disposed in the hollow body to close the opposite ends of the hollow valve seat, and connected to each other by a connecting member.
The first and second valve members may be moved toward either the first or second outlet opening, which has a pressure lower than that of the other outlet opening, due to a pressure difference between the first and second outlet opening, so that a corresponding first or second valve member closes one end of the valve seat adjacent to the other outlet opening with a higher pressure, thereby allowing the inlet opening of the hollow body to communicate with the one outlet opening with lower pressure.
Each of the first and second eccentric units may include an eccentric cam provided on the rotating shaft, an eccentric bush rotatably fitted on an outer surface of the eccentric cam, a corresponding one of the first and second roller pistons being fitted on an outer surface of the eccentric bush, and a stop unit to cause the eccentric bush to be maintained in an eccentric state or in a non-eccentric state.
The stop unit may include a first stop element projected from the eccentric cam, and a second stop element protruded from the eccentric bush to be caught by the first stop element.
Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.